Natural populations of immature Culex pipiens quinquefasciatus will be studied to determine stage-specific mortality rates in various habitats. Natural mortality factors wil be studied to determine which are most importnat in regulating population size. Physical and biological characteristics of breeding places will be studied. Life tables of field populations will be constructed. Pathogenic organisms found will be studied. A model of C. p. quinquefasciatus immature populations will be devloped.